Businesses is the plural of a business when business means a company.
Business’ is the possessive form of the word business.
Business’s is also an accepted possessive form of the word business.
Before we begin to understand the possessive form of the word “business” we need to think about how we use the word.
There are two meanings of the word “business”
The first meaning is uncountable and means to engage in trading with other people.
Let’s do business together.
I often go to Japan on business.
This meaning of business does not have a singular or plural(because it is uncountable) and we don’t need to think about possessive form.
The second meaning of business is as a noun that has the same meaning as a company or enterprise.
I have an online business.
I own different businesses around the world.
This form is can have a plural form as you can count the different businesses that a person can have.
It can also have a possessive form, as a business can own things.
“Businesses” is the plural form of the word business when you are describing a company.
Richard Branson is an entrepreneur who has started many businesses in different fields.
Business’s is one way of writing the singular possessive form of the word business when we are using the “company” form of the word.
Most style guides would use business’ as both the singular and plural possessive form of the word due to the one-syllable rule which you read more about in my article and how to form possessive nuns ending in s here.
Business’ is the possessive plural form of the word business(again when we are using the noun that means a company)
We use the apostrophe after the s because the word “business” ends in s.
An example of this is when we want to talk about a business’ assets.
If you find this difficult(and you are not alone!) you can always say that “X belongs to the business”.
These are the business’ chairs.
These chairs belong to the business.
What do the style guides have to say? (AP, APA, CMS, and MLA)
According to the Chicago Manual of Style, the general rule is to add ’s to a singular noun ending in -s to form the possessive. The AP Style Guide suggests adding only an apostrophe to any word ending in “s” to make it possessive. The Macmillan College Handbook provides a bit of flexibility, allowing for either -‘s or just the apostrophe, especially if the proper noun ends in -s or -z and has two or more syllables ending in the same sound5.
The word company works slightly differently so I wrote a new article about it and you can read that article here.